JPH0853155A - Film which is easily tearable in longitudinal direction - Google Patents

Abstract

PURPOSE:To obtain a uniaxially stretched film comprising compositions containing high density polyethylene which can be easily torn (easily tearable) by hand in the longitudinal direction thereof. CONSTITUTION:A raw film prepared by forming a composition of polymers comprising 99-70 pts.wt. of high density polyethylene and 1-30 pts.wt. of polyolefin, the density of which is 0.94-0.97g/cm<3> and MFR10/MFR2.16 is 10 or less, is stretched to 3-8 times the length thereof in the longitudinal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent film having excellent longitudinal tearability and tear direction, which can be easily cut linearly by hand, and its use.

[0002]

2. Description of the Related Art Conventionally, there is a uniaxially stretched high density polyethylene film as a linear cut film. In addition, JP-A-5
In JP-A-5-3986, (a) density 0.94 g / cm ^{3
~0.97g / cm 3, ASTM-D} -1238-52
Melting index MFR _2.16 measured by the method specified in T
And M measured with a load of 10 kg in this method
95-60 parts by weight of high-density polyethylene having a MFR ₁₀ / MFR _2.16 value of 10 or less calculated from FR ₁₀ and (b) an ethylene-α-olefin random copolymer having an ethylene content of 60-95 mol%. An original film obtained by molding a polymer composition consisting of 5 to 40 parts by weight is
There is a description of a polyolefin film for packaging which is uniaxially stretched in the machine direction at a draw ratio of not less than 2 times and the stretched film is kept to have an elongation at break of 5% or more in the transverse direction. However, JP-A-5
The uniaxially stretched film described in JP-A-5-3986 is not intended for easy tearability, but is intended for lateral twist packaging, and has a small haze value and good twist packaging suitability, but it is intended to tear in the longitudinal direction. Then, elongation called necking occurs in the film, which may make it difficult to tear.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an easily tearable film having a small haze value, which does not cause elongation called necking in the film even when it is torn in the longitudinal direction. Another object of the present application is to provide an easily tearable film in which thin fibrous substances (hereinafter referred to as "whiskers") hardly occur on the surface (cut surface) where the film is torn.

[0004]

The present invention has a density of 0.94.
^{g / cm 3 ~0.97g / cm 3} , ASTM-D-12
MFR ₁₀ / MFR calculated from the melting index MFR _2.16 measured by the method specified in 38-52T and the MFR ₁₀ measured with a load of 10 kg in this method.
_2.16 high density polyethylene (A) with a value of 10 or less
A raw film obtained by molding a polymer composition consisting of 98 to 70 parts by weight and a polyolefin (excluding (A) above) (B) 1 to 30 parts by weight is stretched at a draw ratio of 3 to 8 in the machine direction. The above-mentioned problems are solved by a longitudinal easy-tearable film obtained by stretching. The present invention is also achieved by the following means. Polyolefin is propylene, butene-1, 4 methylpentene-1, hexene-1.
Of the above-mentioned easily tearable film, which is a homopolymer of the above, a copolymer of one of these α-olefins with another α-olefin, or a blend of these polymers. The easily tearable film as described above, wherein the polyolefin is a cyclic olefin polymer. The stretching ratio is 3 to 5 times.
A packaging material for food using the easily tearable film described in any one of 3 to 3.

The present invention will be described in detail below. The high density polyethylene (A) used in the present invention has a density of 0.94 g.
/ Cm ^{3 to} 0.97 g / cm ³ , preferably 0.945
^{g / cm 3 ~0.965g / cm 3} , ASTM-D-1
MFR ₁₀ / MF calculated from the melting index MFR _2.16 measured by the method specified in 238-52T and the MFR ₁₀ measured with a load of 10 kg in this method.
The value of R _2.16 is 10 or less, preferably 9 or less. The amount of high-density polyethylene in the polymer composition is 99 to 70 when the polymer composition ((A) + (B)) is 100 parts by weight.
Parts by weight, preferably 98 to 75 parts by weight.

The polyolefin (B) used in the present invention is
Α-Olefin homopolymers such as propylene, butene-1, 4 methylpentene-1, and hexene-1, or copolymers of one of these α-olefins with one or more other α-olefins. Or a blend of these polymers and / or copolymers. Examples of other α-olefins include ethylene, propylene, butene-1, 4 methylpentene-1, hexene-1, octene-1, nonene-1, decene-1. Preferred is a propylene homopolymer or a propylene / ethylene copolymer. The melting index, density, etc. of the polyolefin are not limited, but the melting index MFR0.1-10, (190
C.) A density of 0.820 to 0.920 is preferable.

A cyclic olefin polymer may be used as the polyolefin (B). The cyclic olefin polymer has a softening temperature of 70 to 200 ° C., preferably 100 to 18 described in JP-A-2-196832.
The intrinsic viscosity measured at 0 ° C and 135 ° C decalin is 0.0.
The amount used is 5 to 10 dl / g, preferably 0.3 to 2.0 dl / g. MFR (260 ° C) is usually 5
The one with 50 g / 10 min is used. Further, the glass transition point is 50 to 100 ° C, preferably 80 to 170 ° C.
The crystallinity by X-ray diffraction method is 0 to 20%, preferably 0 to 2%. This polymer has an ethylene unit of 52 to 90 mol%, preferably 55 to 80%.
And the cyclic olefin unit is 10 to 48%, preferably 2
0 to 45%. Specific examples include a random copolymer of ethylene and tetracyclododecene, and a random copolymer of ethylene and 8-methyltetracyclododecene.

The amount of the polyolefin (B) blended is 1 to 30 parts by weight, preferably 2 to 100 parts by weight of the polymer composition.
25 parts by weight. When the cyclic olefin polymer is used, the object of the present application can be achieved by blending it in a small amount.

If desired, antioxidants, lubricants, slip agents, antiblocking agents, antistatic agents, coloring agents and the like can be added to the polymer composition.

The easily tearable film of the present invention is produced by a usual method. An example of the manufacturing method will be described below. First, the polymer composition is melt extruded from a T-die at 200 to 250 ° C. and cooled to 80 ° C. to 110 ° C. on a cooling roll,
A raw film (thickness: about 100 μm to 500 μm) is formed. This film is stretched at 80 ° C. to 130 ° C. by a roll stretching method in the machine direction 3 to 8 times, preferably 4 to 7 times. Stretching less than 3 times tends to cause uneven thickness in the machine direction, and stretching more than 8 times tends to cause film breakage during production. Further, when a 3 to 8 times stretched film is examined in more detail, a 5 to 7 times stretched film tends to have whiskers on the cut surface, and a 3 to 5 times stretched film hardly causes whiskers. However, if the stretch ratio is low, the Young's modulus is low and the film becomes less stiff.
It is good to use it as 8 times product.

When the stretched film needs to have thermal dimensional stability, it is preferable to shrink the film in the machine direction at 80 ° C. to 130 ° C. for 1 to 10%. If necessary, the surface of the film may be subjected to surface treatment such as corona treatment.

The film of the present invention has a thickness of 15 μm to 1 μm.
The thickness is 50 μm, preferably 20 μm to 50 μm, the linear cut property is good, and the haze is usually 30% or less, preferably 20% or less, and more preferably 10% or less. When the stretching ratio is low, there is no whiskers.

[0013]

Examples 1 to 8 and Comparative Examples 1 to 4 The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The composition of resin (1) and resin (2) to (5) described below is used, and for comparison, only resin (1) is used and the composition of resin (1) and resin (6) is used. If so, the film was formed and stretched. (1) High density polyethylene (expressed as HDPE) [MFR
(190 ° C) = 1.0g / 10min, MFR ₁₀ / MF
R _2.16 = 9.0, density 0.96 g / cm ³ ]. (2) Homopolypropylene (denoted as PP) [MFR (2
30 ° C.) = 2.0 g / 10 min, density 0.91 g / c
m ³ ]. (3) Polybutene-1 (denoted as PB) [MFR (190
C.) = 1.8 g / 10 min, melting point 125.degree. C.]. (4) Polypropylene co-polymer (denoted as CoPP)
[MFR (230 ° C.) = 1.4 g / 10 min, melting point 1
39 ° C]. (5) Cyclic olefin polymer (Mitsui Petrochemical Co., Ltd .: Apel registered trademark) [MFR (260 ° C.) = 40
g / 10 min, density 1.02 g / cm ³ , softening point 90
° C]. (6) Ethylene-α-olefin co-polymer (denoted by TF) [MFR (190 ° C.) = 4.0 g / 10 min,
Density 0.88 g / cm ³ ].

Using the above resin or composition, the film was formed and stretched by the T-die method under the conditions shown in Table 1.

[Table 1]

The physical properties and performance of the stretched film obtained by the above method were measured by the following test methods. (1) Tensile test: Measured according to JIS Z1702. (2) Straight line cutting property The sample is cut in the lengthwise direction to a size of A-4. Make a 3 cm cut with a width of 2 cm in the center to tear in the length direction. Place it on a flat table, pick up the central part with a width of 2 cm, press both sides with the other hand, and pull it in the direction of 180 degrees to the film at a speed of 1 m / min. Evaluation of rectilinearity Tear with almost the same width ○ Film stretches and bends × Evaluation of cut surface No beard on cut surface ○ Whisker on cut surface × (3) Haze ASTM D-1003 According to the above, four films were stacked and measured.

The measurement results are shown in Tables 2 and 3.

[Table 2]

[Table 3]

[0017]

EFFECT OF THE INVENTION The stretched film of the present invention has (1) a small haze, (2) a good linear cutting property for tearing while maintaining strength such as tensile strength, and (3) a whisker for a low stretch ratio. Absent. Therefore, it is used as a packaging material for food such as vegetables, fruits, confectionery, rice balls and hand towels.

[Short description of table]

[Table 1] A table showing film forming and stretching conditions.

[Table 2]

Table 3 is a table showing measurement results of physical properties and performance of the film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location C08L 23/18 // B29K 23:00 (72) Inventor Hiromi Suzuki 9 Kitatone, Sowa-cho, Sarushima-gun, Ibaraki Prefecture Tohcello Co., Ltd. Ibaraki Factory

Claims (4)

[Claims] 1. A density of 0.94 g / cm ^{3 to} 0.97 g /
cm ³ , MFR _2.16 measured by the method specified in ASTM-D-1238-52T, and in this method,
99-70 parts by weight of a high-density polyethylene (A) having a MFR ₁₀ / MFR _2.16 value of 10 or less and a polyolefin (excluding the above (A)) (B) calculated from MFR ₁₀ measured with a load of 10 kg ) A longitudinal direction easily tearable film obtained by stretching a raw film obtained by molding a polymer composition consisting of 1 to 30 parts by weight in the longitudinal direction at a stretching ratio of 3 to 8 times. 2. The polyolefin is a homopolymer of propylene, butene-1,4 methylpentene-1, hexene-1, or one or more other α-olefins containing one of these α-olefins as a main component. The easily tearable film according to claim 1, which is a copolymer thereof with or a blend of these polymers. 3. The easily tearable film according to claim 1, wherein the polyolefin is a cyclic olefin polymer. 4. A packaging material for food using the easily tearable film according to claim 1, which has a draw ratio of 3 to 5 times.